1. Field
The present disclosure relates to a control rod drive mechanism built in a nuclear reactor, which is configured with a coil housing substituting for a latch housing of a latch assembly, to miniaturize the control rod drive mechanism built in the nuclear reactor and thus to secure a sufficient fluid passage of a reactor coolant as well as to enhance space efficiency, and also configured to improve an operating load carrying path of the latch assembly so that the coil housing supports only the weight of a coil, a load of the reactor coolant and a load applied to the coil.
2. Discussion of Related Art
In a control rod drive mechanism built in a nuclear reactor, the Westinghouse Electric Corporation has proposed a configuration using a coil used at a high temperature, which is disclosed in U.S. Patent Application Publication No. 2012/0148007 A1. Here, a drive rod housing is formed of a non-magnetic material to have the same configuration as the housing of the control rod drive mechanism of an existing commercial nuclear reactor, and applied to a design thereof.
However, in spite of the above-mentioned improvement, the control rod drive mechanism built in the nuclear reactor, in which the housing of the control rod drive mechanism or the housing of the latch assembly does not serve as a pressure vessel, also has a housing in which a concept and size are similar to those the housing of the control rod drive mechanism applied to a current commercial nuclear reactor, and thus space efficiency of the control rod drive mechanism and the nuclear reactor is degraded.
Further, in a configuration in which the housing of the latch assembly is formed of one magnetic material or non-magnetic material and installed to extend in a lengthwise direction of the latch assembly, it is impossible to optimize formation of a magnetic field and thus to maximally generate a lifting force.
Also, in the current nuclear reactor, two kinds of methods, i.e., a method of controlling an insertion level of the control rod into the core and a controlling method by injection of a boric acid solution, are used to control reactivity of a reactor core, and thus the control rod need not be inserted into all nuclear fuel.
However, since a large amount of radioactive waste is discharged in the method of controlling the reactivity of the reactor core using the boric acid solution, a nuclear reactor having the boron-free core which controls the reactivity using only the control rod drive mechanism is being developed. To this end, the control rod should be installed and controlled at most of the nuclear fuel.
However, since a size of the current control rod drive mechanism is larger than or the same as a size of a single nuclear fuel, it is impossible to install more control rod drive mechanisms at the current commercial nuclear reactor, and thus it is necessary to reduce the size of the control rod drive mechanism.
Further, in the control rod drive mechanism built in the nuclear reactor, a driving force generating mechanism (particularly, an electromagnet) should be cooled by the reactor coolant, and thus to secure a fluid passage of the reactor coolant flowing around the control rod drive mechanism, it is urgently required to develop a device which may realize miniaturization of the control rod drive mechanism.